Conventionally, there is known an article transfer device which is configured to capture, by an image capturing device, an image of a plurality of workpieces which are randomly placed on a conveyor and which are moved by operation of the conveyor, and to perform a workpiece picking by a robot by using the image captured by the image capturing device (for example, see PTL 1). The article transfer device is configured to detect a workpiece in a captured image, to set a proximity state determination region around each detected workpiece, and to determine whether there is another detected workpiece in the proximity state determination region.